REPORT ON METEOROLOGICAL OBSERVATIONS, WISLEY, 1914. 87 



which the monthly means of the Wisley observations could be 

 compared ; but eventually several sets of observations of varying 

 duration, and made at places lying in different directions and at 

 varying distances from the Gardens, were secured, and from these, 

 after careful comparison and consideration, a set of averages was 

 deduced which it was hoped approximated fairly closely to the true 

 average values for Wisley ; and the monthly means published in 

 these Reports have hitherto been compared with them. 



But with the close of the year 1913 there became available observa- 

 tions made at the Gardens, under conditions carefully designed to 

 secure accuracy, and extending over a period of ten years ; and from 

 them a new set of average values of temperature and rainfall have 

 been calculated, and they have been used for the first time in preparing 

 the Report for 1914. It is of interest now to see how closely these 

 new averages agree with those hitherto used ; and when it is 

 remembered that the data previously available were very much of 

 the nature of disjecta membra, from different localities and for various 

 years, the agreement is rather remarkable. 



As regards temperature, the difference between the two sets of 

 monthly averages is less than half a degree in six of the twelve months, 

 does not exceed one degree in two others, and is below two degrees 

 in three of the remaining four. The greatest difference is 2'J degrees 

 in December, probably owing to an exceptionally cold year having 

 been embraced in the earlier series. In almost every case the new 

 Wisley averages are higher than the former set. 



W r ith regard to rainfall, bearing in mind the frequently local 

 character of the phenomenon, and the wide variation in its intensity 

 commonly found at places only a short distance from each other, 

 a very close agreement was scarcely hoped for ; nevertheless, in 

 two months the two averages are alike ; in six others the difference 

 between them is less than half an inch ; whilst in the remaining four 

 months it lies between three-quarters of an inch and an inch. It is, 

 however, somewhat curious that in the ten months which show 

 differences between the two means the differences alternate regularly 

 between minus and plus; e.g., in May the new (Wisley) average total 

 is 0*45 inch less than the total formerly used, whilst in June it is 0*32 

 inch more ; and the result is that the new yearly total differs only ri 

 inch, or 4 J per cent., from the total formerly adopted. It is scarcely 

 probable that observations of rainfall made at the same place, in two 

 successive decennial periods, would show a closer agreement. 



